Since when did Tahm's Devourer ending give a moment of invunerability?

So I'm playing Evelynn in this game, and I come upon the adc and tahm near the baron pit. HE automatically swallows her. I wait it out knowing she is dead to rights to my ult because she has like maybe 300 hp. I see him spit her out and she is standing in the river clear as day. And I ult her. Take note, she is not on the edge of my ult where I might miss. She is full blown in the middle of it. And she doesn't die. She takes the full hit clear as day and doesn't die. I wasn't exhausted. She didn't have GA. She didn't have a stopwatch or any variation of. There was no Guardian to proc. No redemption. No Locket near her. She literally had nothing to save her. And yet she took no damage while being right in my ult. And she was freshly spit out of tahm. Like a second after he spit her out. The missed Q was because he devourered her a second before I threw it before people get on to me about that.

https://www.youtube.com/watch?v=P7BBnOPKfqM&feature=youtu.be